Studies of Helical Aggregates of Molecules. III. The Bivalent Metal Soaps of Optically Active 12-Hydroxyoctadecanoic Acid

Abstract

The bivalent metal soaps of optically-active 12-hydroxyoctadecanoic acid were found to crystallize out in the form of twisted fibers from aqueous or anhydrous ethanol solutions. Most soaps of this class produced both righthanded and left-handed fibers from the same specimen, more of the latter in the case of the D-enantiomer. An enantiomorphic relationship of the sense of twist was clearly demonstrated by using both enantiomers of the Ca soap. Under a high-resolution electron microscope, it was observed on the Sr soap that Sr atoms are arranged in lines along the fiber axis with a periodicity of 33–40 Å, showing that the hydroxyoctadecanoate chains of the soap molecules are aligned approximately parallel to the width of the fiber. The twisting of the soap fibers was associated with the layer structure characteristic of soap.